Light on its feet when not slipping in dewy pools of emotional catharsis, Jonathan Kasdan’s first feature — after years of working on premium TV shows like “Freaks and Geeks” and “Dawson’s Creek” — is above-average date-night fodder. Though often prone to what can be called “The Zach Braff Effect,” its story is geometrically ideal.

Carter Webb (Adam Brody of “The O.C.”), a 20-something writer for a soft-core cable show, gets dumped by his glamorous Spanish actress girlfriend, freaks out, and decides to go back to the ancestral home in suburban Michigan to take care of his wacky, ailing grandma (the inevitable Olympia Dukakis).

Carter’s deeper motive is to finally write that saga about his coming-ofage at a fancy West Los Angeles high school, but he never gets around to that. Instead, he gradually becomes involved with the family across the street: Sarah (Meg Ryan), a 40-year-old housewife with a terrible secret, and her two daughters, the teenage Lucy (Kristen Stewart) and her precocious little sister, Paige (Makenzie Vega).

There is, nominally, a husband, who functions mostly as wallpaper. That’s part of the reason Sarah is so drawn to Carter. She’s spent her life becoming a model wife and mother, but she suddenly finds herself in crisis mode, wondering if it’s all been enough for a proper legacy. Carter, comically bereft over his trendy girlfriend’s departure, discovers in Sarah something fresh, honest, and appealing.

Meanwhile, Lucy, who is attracted to Carter’s seemingly hip, big city status, begins to confide in him as well, seeking advice on her high school relationships (Mr. Brody plays the character as clever and good-looking, but with a serious dorky streak, not unlike his character in “The O.C.”). As they spend more time hanging out, they become emotionally dependent on each other, brought closer by the unforeseen life-threatening event that soon is to hover over everyone’s head. Soon enough, Carter is in the middle of an unusual love triangle in which everyone is trying madly to connect and resolve their deep, gnawing issues — with a smartly curated soundtrack, a surplus of adolescent trauma, and Ms. Dukakis pretending to be senile.

Except for that last part, all of this actually works — even though Mr. Kasdan, the son of veteran director Lawrence Kasdan, has written a screenplay that is so annoyingly tight and shapely he should adapt it as software. Why it works has a lot to do with the cast. Mr. Brody makes himself a winning comic foil for his character’s obsessions, though this version of the aspiring writer flown home for inspiration seems almost too wise beyond his years. In the same way, Ms. Ryan could not appear more huggable, even though she appears to have had Michelle Pfeiffer’s lips transplanted onto her face.

Mostly, though, the movie belongs to the kids. Maybe it’s all that time logged on “Dawson’s Creek,” but the 26-year-old Mr. Kasdan has a credible ease writing for young actors. Ms. Stewart has that budding, coltish thing going on, and makes teenage angst feel nail-bitingly true. And Ms. Vega, who plays the world’s most impossibly mature 11-year-old, offers a vivid pipeline into childhood hope and persistence. Even when the story should become cloying, the performances sustain a sense of emotional honesty.

The movie needs that, because in many ways its vision of Middle America is that of an overly idealized Caucasian wonderworld that could only exist on the screen, big or small. The worst thing kids do to one another is throw beer and pick fights at parties, and bug their parents by sneaking out at night to cruise around in hopped-up convertibles, smoking cigarettes and playing loud music. “In the Land of Women” looks an awful lot like the place a Hollywood insider wishes he could go home to again. The state of Michigan should adopt this movie as its mascot.